European Patent Specification EP No. 0077135A corresponding to U.S. Pat. No. 4,534,015 and copending European Patent Application No. 84301981.1 corresponding to U.S. Ser. No. 591,939, now U.S. Pat. No. 4,627,019 describe memories employing a film comprising a plurality of monomolecular layers. In the case of EP No. 0077135A the film is described as being formed by the Langmuir-Blodgett technique, and in the case of the European Patent Application at least one of the layers is formed by a process of chemisorption. In these memories each layer is capable of carrying a charge. A charge injector is located on one side of the film for introducing charges into the film in a time sequence which corresponds to the information to be carried. Means are provided for applying a voltage between the faces of the film to cause the charge carried by any larger to be transferred to the adjacent layer. The sequence of charges carried by the film may be read out by a photon-emitting electron arrival detector or by a method of current differentiation. At least some of the layers of the film are preferably formed of a polydiacetylene (PDA), though other materials may be used, for example a porphyrin.
The charge injector described in the above mentioned specification and application takes the form of a photoinjector layer which injects charge into the adjacent film layer in response to incident photons. The present invention provides a memory of the same type as that described in the above-mentioned European specification and application (the disclosures of which are incorporated herein by reference) but with a charge injector which does not require a source of photons.